1. Field of Invention
This invention relates to the design and manufacturing of dual-modular actuators that have a common axis of rotation and are suitable for use in hard disk drives and other data storage devices where high I/O performance is desirable.
2. Description of Prior Art
Rotary actuators made their introduction into disk-drives in the early 1980""s replacing the more complex linear actuators with a more cost-effective assembly. However, the critical air-bearing surfaces, that controls the spacing between the read/write transducer and the media (flying height) had to be radically redesigned to accommodate the yaw angles introduced to the slider by rotation about a pivot point. The flying height is the most critical parameter to high areal density recording (bit density times track density) and any part of the actuator design that limits it is unacceptable.
Today""s implementation of rotary actuators is filled with major problems that degrade flying height and therefore limit areal density and performance. Some of the more salient problems are:
(a) mechanical resonances, in the actuator subsystem, that cause off-track motion at the heads, adversely affecting servo performance.
(b) out of plane distortions in the spiral coil during high current (seek) operation that cause acoustic noise and distract from audio/video presentations. This is totally unacceptable in today""s emerging audio/video markets;
(c) distortions of the arm""s mounting surfaces caused by the mechanical xe2x80x9cball swagingxe2x80x9d of HGA attachment;
(d) poor head to disk spacing control for multi-head actuators;
The critical assemblies of today""s multi-part actuators are extremely labor intensive and do not lend themselves to precision automated tooling. Extensive rework procedures are common and quality issues are prevalent.
A way to dramatically increase the I/O performance of the disk drive is the addition of another independent actuator. Dual-actuators were used in all IBM drives starting in the mid 1970""s and continuing until the early 1990""s. Each drive had two linear actuators with each actuator having access to half the data contained in the drive. In the 1980""s, Conner Peripherals introduced a dual rotary actuator 3.5-inch drive with impressive I/O performance specifications. However, it also employed separate actuators, located on opposite sides of the disk assembly, and therefore could not be packaged in the standard 3.5-inch form factor. It also had significantly higher costs than a single actuator design and was quickly removed from the market. This inability to provide dual-actuator performance within the form factor of today""s disk drives, especially height, is a major limitation of today""s rotary actuators.
Objects and Advantages
Accordingly, several objects and advantages of my invention are;
(a) a thin ceramic arm assembly that combines the spiral coil, HGA, IC and Flex Cable interconnects and is manufactured by high-volume semiconductor processes;
(b) a thin ceramic arm assembly exhibiting higher mechanical resonances thus allowing higher track and bit densities;
(c) ceramic arms, having very high stiffness, that eliminate out of plane spiral coil distortions, thus eliminating acoustic noise;
(d) metal pads on the ceramic arm s that allows laser welding of the HGA to the arms;
(e) precise and automated assembly of arms, to ceramic bearing sleeve, to form modular actuators assemblies, having a low moment of inertia;
(f) arm manufacturing and assembly can be automated eliminating expensive labor content;
(g) the stacking of multiple modular-actuators, on a common shaft, and which can rotate independently of each other;
(h) a Voice Coil Motor (VCM), having multiple magnetic circuits, to interact with the coil structure of each modular-actuator assembly;
(i) a low profile rotary dual-actuator assembly that can replace single rotary actuator assemblies on a 1:1 basis;
Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing descriptions.